The invention concerns a contact roll for belt grinding machines with a steel core and a surrounding sleeve comprising an intermediate layer of elastically yieldable material, at least partially covering the steel core, and a plurality of elements of a hard material arranged on the outer surface of the intermediate layer and intended to engage the grinding belt.
German Gebrauchsmuster 1 953 917 discloses a contact roll in which a steel core is surrounded by a rubber sleeve. This rubber sleeve can be armored or provided with a different profile. The rubber sleeve can also consist of layers of different Shore hardness.
On the other hand there are also known contact rolls which have a steel sleeve. It is entirely common to find with these known rolls from the state of the art that rolls with a relatively soft outer surface possess a high tolerance for irregularities in the work pieces, but they also result in only a low degree of abrasion since the grinding belt is not pressed to the work piece with the required amount of force. Such rolls are not suited to the achievement of high cutting efficiency with metallic work pieces. In contrast to this there have been provided rolls with a hard outer surface, that is for example a steel sleeve, providing a high amount of abrasion per unit of time. These however have only a small tolerance for work pieces with not entirely flat surfaces.
To solve these problems there has already been proposed, in U.S. Pat. No. 2,162,279, a pressure roll of the aforementioned type wherein outer elements of hard material are formed as blocks of hard rubber, cork or steel and are fastened to an intermediate layer of soft rubber surrounding the core, and which elements are moveable independently of one another. These pressure rolls make possible a good tolerance for uneven work pieces. A disadvantage of this solution is, however, that because of the independent moveability of the block type elements on one hand unbalances can appear and on the other hand the elements, when attempting to achieve a high rate of abrasion, can set up large shear forces. These shear forces can in turn lead to a ripping of the elements from the intermediate layer.